The archaeologists aren't sure why the children were sacrificed, but it may have to do with a severe El Niño event the same year.

Archaeologists have found the remains of 140 children in a mass grave on the northern coast of Peru — evidence they say suggests the largest ritual child sacrifice in history, according to National Geographic.

The gruesome scene also contained the skeletons of 200 baby llamas. Researchers estimate the event likely occurred around 550 years ago, when the area was controlled by the Chimú Empire, the second largest pre-Columbian society behind the Incas.

"I, for one, never expected it," John Verano, an anthropologist at Tulane University who worked on the dig, told National Geographic. "And I don't think anyone else would have, either."

Archaeologists were first alerted to the human remains after residents of the Peruvian city of Trujillo found weathered skeletons protruding from a bluff near their houses in the La Libertad neighborhood in 2011. During a dig that year, archaeologists found the remains of 42 children, a number that has since increased.

17PHOTOS

Huanchaquito-Las Llamas -- mass grave site in Peru

See Gallery

Huanchaquito-Las Llamas -- mass grave site in Peru

An archaeologist catalogs the bones of a camelid, part of unearthed archaeological remains found at tombs of children belonging to the Chimu culture, sacrificed approximately 800 years ago in the fishing town of Huanchaquito, Trujillo, September 13, 2011. Archaeologists unearthed the remains of 42 children and 74 camelids, part of a massive sacrifice that formed part of a religious ceremony of the pre-Inca Chimu culture for the fertility of the ocean and the land, and it represents the most important discovery related to human and animal sacrifices of the Chimu culture in terms of numbers of excavated individuals, according to Oscar Gabriel Prieto, chief archaeologist of the archaeological project. Picture taken September 13, 2011. REUTERS/Mariana Bazo (PERU - Tags: SOCIETY ANIMALS RELIGION SCIENCE TECHNOLOGY TRAVEL)

Archaeologist Oscar Gabriel Prieto points to the remains of a child, part of the 42 children and 74 camelids remains unearthed that were sacrificed approximately 800 years ago in the fishing town of Huanchaquito, Trujillo September 13, 2011. Archaeologists unearthed the remains of 42 children and 74 camelids, part of a massive sacrifice that formed part of a religious ceremony of the pre-Inca Chimu culture for the fertility of the ocean and the land, and it represents the most important discovery related to human and animal sacrifices of the Chimu culture in terms of numbers of excavated individuals, according to Oscar Gabriel Prieto, chief archaeologist of the archaeological project. Picture taken September 13, 2011. REUTERS/Mariana Bazo (PERU - Tags: SOCIETY RELIGION SCIENCE TECHNOLOGY TRAVEL)

Local villagers look on as archaeologists clean the unearthed remains of 42 children and 74 camelids, sacrificed approximately 800 years ago and found in the fishing town of Huanchaquito, Trujillo September 13, 2011. The massive sacrifice were part of a religious ceremony of the pre-inca Chimu culture for the fertility of the ocean and the land, and it represents the most important discovery related to human and animal sacrifices of the Chimu culture in terms of numbers of excavated individuals, according to Oscar Gabriel Prieto, chief archaeologist of the archaeological project. Picture taken September 13, 2011. REUTERS/Mariana Bazo(PERU - Tags: SOCIETY RELIGION SCIENCE TECHNOLOGY TRAVEL)

The remains of a child and a camelid are seen, part of the 42 children and 74 camelids remains unearthed that were sacrificed approximately 800 years ago in the fishing town of Huanchaquito, Trujillo September 13, 2011. Archaeologists unearthed the remains of 42 children and 74 camelids, part of a massive sacrifice that formed part of a religious ceremony of the pre-Inca Chimu culture for the fertility of the ocean and the land, and it represents the most important discovery related to human and animal sacrifices of the Chimu culture in terms of numbers of excavated individuals, according to Oscar Gabriel Prieto, chief archaeologist of the archaeological project. Picture taken September 13, 2011. REUTERS/Mariana Bazo (PERU - Tags: SOCIETY RELIGION SCIENCE TECHNOLOGY TRAVEL ANIMALS)

An archaeologist catalogs the bones of a camelid, part of unearthed archaeological remains found at tombs of children belonging to the Chimu culture, sacrificed approximately 800 years ago in the fishing town of Huanchaquito, Trujillo, September 13, 2011. Archaeologists unearthed the remains of 42 children and 74 camelids, part of a massive sacrifice that formed part of a religious ceremony of the pre-Inca Chimu culture for the fertility of the ocean and the land, and it represents the most important discovery related to human and animal sacrifices of the Chimu culture in terms of numbers of excavated individuals, according to Oscar Gabriel Prieto, chief archaeologist of the archaeological project. Picture taken September 13, 2011. REUTERS/Mariana Bazo (PERU - Tags: SOCIETY ANIMALS RELIGION SCIENCE TECHNOLOGY TRAVEL)

The remains of a child is seen, part of the 42 children and 74 camelids remains unearthed that were sacrificed approximately 800 years ago in the fishing town of Huanchaquito, Trujillo September 13, 2011. Archaeologists unearthed the remains of 42 children and 74 camelids, part of a massive sacrifice that formed part of a religious ceremony of the pre-Inca Chimu culture for the fertility of the ocean and the land, and it represents the most important discovery related to human and animal sacrifices of the Chimu culture in terms of numbers of excavated individuals, according to Oscar Gabriel Prieto, chief archaeologist of the archaeological project. Picture taken September 13, 2011. REUTERS/Mariana Bazo (PERU - Tags: SOCIETY RELIGION SCIENCE TECHNOLOGY TRAVEL)

Archaeological students clean some of the unearthed remains of 42 children and 74 camelids, sacrificed approximately 800 years ago and found in the fishing town of Huanchaquito, Trujillo September 13, 2011. The massive sacrifice were part of a religious ceremony of the pre-inca Chimu culture for the fertility of the ocean and the land, and it represents the most important discovery related to human and animal sacrifices of the Chimu culture in terms of numbers of excavated individuals, according to Oscar Gabriel Prieto, chief archaeologist of the archaeological project. Picture taken September 13, 2011. REUTERS/Mariana Bazo (PERU - Tags: SOCIETY RELIGION SCIENCE TECHNOLOGY TRAVEL)

The remains of a child is seen, part of the 42 children and 74 camelids remains unearthed that were sacrificed approximately 800 years ago in the fishing town of Huanchaquito, Trujillo September 13, 2011. Archaeologists unearthed the remains of 42 children and 74 camelids, part of a massive sacrifice that formed part of a religious ceremony of the pre-Inca Chimu culture for the fertility of the ocean and the land, and it represents the most important discovery related to human and animal sacrifices of the Chimu culture in terms of numbers of excavated individuals, according to Oscar Gabriel Prieto, chief archaeologist of the archaeological project. Picture taken September 13, 2011. REUTERS/Mariana Bazo (PERU - Tags: SOCIETY RELIGION SCIENCE TECHNOLOGY TRAVEL)

Archaeological students clean unearthed remains of 42 children and 74 camelids, sacrificed approximately 800 years ago and found in the fishing town of Huanchaquito, Trujillo September 13, 2011. The massive sacrifice were part of a religious ceremony of the pre-inca Chimu culture for the fertility of the ocean and the land, and it represents the most important discovery related to human and animal sacrifices of the Chimu culture in terms of numbers of excavated individuals, according to Oscar Gabriel Prieto, chief archaeologist of the archaeological project. Picture taken September 13, 2011. REUTERS/Mariana Bazo (PERU - Tags: SOCIETY RELIGION SCIENCE TECHNOLOGY TRAVEL)

An archaeological student cleans one of the unearthed remains of 42 children and 74 camelids, sacrificed approximately 800 years ago and found in the fishing town of Huanchaquito, Trujillo September 13, 2011. The massive sacrifice were part of a religious ceremony of the pre-inca Chimu culture for the fertility of the ocean and the land, and it represents the most important discovery related to human and animal sacrifices of the Chimu culture in terms of numbers of excavated individuals, according to Oscar Gabriel Prieto, chief archaeologist of the archaeological project. Picture taken September 13, 2011. REUTERS/Mariana Bazo (PERU - Tags: SOCIETY RELIGION SCIENCE TECHNOLOGY TRAVEL)

An archaeologist collects unearthed remains of 42 children and 74 camelids, sacrificed approximately 800 years ago and found in the fishing town of Huanchaquito, Trujillo September 13, 2011. The massive sacrifice were part of a religious ceremony of the pre-inca Chimu culture for the fertility of the ocean and the land, and it represents the most important discovery related to human and animal sacrifices of the Chimu culture in terms of numbers of excavated individuals, according to Oscar Gabriel Prieto, chief archaeologist of the archaeological project. Picture taken September 13, 2011. REUTERS/Mariana Bazo (PERU - Tags: SOCIETY RELIGION SCIENCE TECHNOLOGY TRAVEL)

An archaeological student cleans one of the unearthed remains of 42 children and 74 camelids, sacrificed approximately 800 years ago and found in the fishing town of Huanchaquito, Trujillo September 13, 2011. The massive sacrifice were part of a religious ceremony of the pre-inca Chimu culture for the fertility of the ocean and the land, and it represents the most important discovery related to human and animal sacrifices of the Chimu culture in terms of numbers of excavated individuals, according to Oscar Gabriel Prieto, chief archaeologist of the archaeological project. Picture taken September 13, 2011. REUTERS/Mariana Bazo (PERU - Tags: SOCIETY RELIGION SCIENCE TECHNOLOGY TRAVEL)

An archaeological student cleans one of the unearthed remains of 42 children and 74 camelids sacrificed approximately 800 years ago and found in the fishing town of Huanchaquito, Trujillo September 13, 2011. The massive sacrifice were part of a religious ceremony of the pre-inca Chimu culture for the fertility of the ocean and the land, and it represents the most important discovery related to human and animal sacrifices of the Chimu culture in terms of numbers of excavated individuals, according to Oscar Gabriel Prieto, chief archaeologist of the archaeological project. Picture taken September 13, 2011. REUTERS/Mariana Bazo(PERU - Tags: SOCIETY RELIGION SCIENCE TECHNOLOGY TRAVEL)

A local villager observes as archaeologists clean the unearthed remains of 42 children and 74 camelids, sacrificed approximately 800 years ago and found in the fishing town of Huanchaquito, Trujillo September 13, 2011. The massive sacrifice were part of a religious ceremony of the pre-inca Chimu culture for the fertility of the ocean and the land, and it represents the most important discovery related to human and animal sacrifices of the Chimu culture in terms of numbers of excavated individuals, according to Oscar Gabriel Prieto, chief archaeologist of the archaeological project. Picture taken September 13, 2011. REUTERS/Mariana Bazo(PERU - Tags: SOCIETY RELIGION SCIENCE TECHNOLOGY TRAVEL)

The remains of a child is seen, part of the 42 children and 74 camelids remains unearthed that were sacrificed approximately 800 years ago in the fishing town of Huanchaquito, Trujillo September 13, 2011. Archaeologists unearthed the remains of 42 children and 74 camelids, part of a massive sacrifice that formed part of a religious ceremony of the pre-Inca Chimu culture for the fertility of the ocean and the land, and it represents the most important discovery related to human and animal sacrifices of the Chimu culture in terms of numbers of excavated individuals, according to Oscar Gabriel Prieto, chief archaeologist of the archaeological project. Picture taken September 13, 2011. REUTERS/Mariana Bazo (PERU - Tags: SOCIETY RELIGION SCIENCE TECHNOLOGY TRAVEL)

Archaeologist Oscar Gabriel Prieto shows the archaeological remains of a child, part of the 42 children and 74 camelids remains unearthed, that were sacrificed approximately 800 years ago in the fishing town of Huanchaquito, Trujillo September 13, 2011. Archaeologists unearthed the remains of 42 children and 74 camelids, part of a massive sacrifice that formed part of a religious ceremony of the pre-Inca Chimu culture for the fertility of the ocean and the land, and it represents the most important discovery related to human and animal sacrifices of the Chimu culture in terms of numbers of excavated individuals, according to Oscar Gabriel Prieto, chief archaeologist of the archaeological project. Picture taken September 13, 2011. REUTERS/Mariana Bazo (PERU - Tags: SOCIETY RELIGION SCIENCE TECHNOLOGY TRAVEL)

Up Next

See Gallery

Discover More Like This

HIDE CAPTION

SHOW CAPTION

of

SEE ALL

BACK TO SLIDE

The site is formally called Huanchaquito-Las Llamas and falls within a residential neighborhood.

Verano is now working with Gabriel Prieto, an archaeologist at the Universidad Nacional de Trujillo, to publish their findings in a peer-reviewed, scientific journal.

Other South American civilizations, like the Incas and the Aztec, practiced ritual human sacrifice, but archaeologists have never found children's bodies in such a high concentration before.

The gruesome details of the slaughter

The details of the slaughter are disturbing. The children mostly ranged from around eight to twelve years old (though the youngest were five). The findings suggest they had their faces smeared with a red pigment, and the skeletons show signs of mutilation, including broken sternums and notches cut into the rib-cages. It seems the children's chests were cut open and their ribs dislocated in order to remove their hearts.

By examining layers of sediment and footprints around the site, the archaeologists concluded that the sacrifices were likely carried out over the course of a single day.

From the footprints, it appears that the children and llamas were led in a single line and sacrificed one after the other. There are even skid marks in the sediment indicating places where the sacrificial victims were reluctant to participate.

The children's bodies were buried facing west, towards the Pacific Ocean, while the llamas were buried facing east, toward the Andes mountains.

Along with the children's remains, archaeologists uncovered the bodies of one man and two women near the sacrificial site. The researchers think the adults may have performed the ritual killings then were executed shortly after.

The precise cuts on the skeletons indicate that the killings were performed by trained hands, according to National Geographic's report.

"It is ritual killing, and it's very systematic," Verano told National Geographic.

The killings could have been in response to an El Niño event

The researchers are now trying to figure out why these children were sacrificed. One theory: bad weather.

In the layers of sediment at the site, researchers found evidence that the region had experienced severe rainfall and flooding around the same time as the sacrifices, likely due to elevated sea temperatures from an El Niño event. The floods may have disrupted the region's agriculture, which could have led to mass starvation.

Child sacrifice may have been a last resort in the hopes that the gesture would improve the weather by appeasing the gods.

The Chimú empire once stretched across a huge swath of South America's Pacific coast, including current-day Peru, Ecuador, and Chile. But the archaeological record suggests they succumbed to an Incan invasion only a few decades after the sacrifices occurred.

"It makes you wonder how many other sites like this there may be out there in the area for future research," Prieto told National Geographic. "This just may be the tip of the iceberg."